Rosacea is a common chronic inflammatory dermatosis characterized according to form by the presence of erythema, telangiectasias, edema, papules, pustules, ocular lesions and occasionally rhinophyma. It is most often bilateral and it affects predominantly the median portion of the face, the forehead, the nose, the chin and the cheeks.
Rosacea generally develops in adults aged 30 to 50 years and is much more common among people with fair skin. It affects women more particularly, although this affection is generally more severe in men. Rosacea is chronic and persists for years with periods of exacerbation and remission.
The pathogenesis of rosacea is poorly understood. Many factors may be involved, such as, for example, psychological factors, environmental factors (sun exposure, temperature, humidity), emotional factors (stress), food-related factors (alcohol, spices), hormonal, gastrointestinal and vascular disorders, even infection by Helicobacter pylori and the characteristic presence of the parasite Demodex folliculorum or Demodex brevis among rosacea patients.
Rosacea can be Classified as Follows:
                Type I: Erythematotelangiectatic rosacea, mainly characterized by persistent central facial erythema and episodic reddening or flushing. Often, this type is also characterized by edema, roughness or scaling and the appearance of dilated blood vessels (telangiectasia) as well as by burning and stinging sensations.        Type II: Papulopustular rosacea, characterized by persistent central facial erythema and by the appearance of transient central facial papules or pustules. These symptoms are sometimes accompanied by burning and stinging sensations. This type may follow or occur in combination with type I.        Type III: Phymatous rosacea, marked by thickening skin and the appearance of irregular nodules. Although the nose is often the most affected area, becoming very large and swollen (“rhinophyma”), other locations are also observed: the chin, the forehead, the cheeks and the ears. This type can follow or occur in combination with type I and II.        Type IV: Ocular rosacea, characterized by red, irritated eyes which may be watery and bloodshot. Symptoms may include the sensation of having a foreign body in the eye, excessive watering, light sensitivity, blurred vision, a sensation of burning, dryness or stinging, itching and alacrima.        
Classically, rosacea can be treated orally or topically with antibiotics such as tetracyclines, erythromycin, clindamycin, but also with vitamin A, salicylic acid, antifungal agents, steroids, metronidazole or with isotretinoin for severe forms or with azelaic acid. However, the use of these antibiotics does not make it possible to effectively treat and/or prevent all the symptoms associated with rosacea and can often cause side effects and intolerance problems in many patients.
Rosacea can also be treated topically using ivermectin to target the parasite Demodex folliculorum or Demodex brevis as proposed in the patent U.S. Pat. No. 5,952,372. However, the effects of resistance of this parasite to ivermectin may occur, thus decreasing the efficacy of such a treatment or making it ineffective.
Thus, it must be acknowledged that there exists a need to provide a more effective rosacea treatment that does not cause side effects and intolerance problems for the patient. In particular, there is to date no rosacea treatment that can replace those that have become less effective or ineffective due to resistance phenomena.